Earlier this year, Apple quietly acquired BookLamp, an interesting start-up out of Boise, Idaho. BookLamp built something called the Book Genome Project, which essentially does for books what Pandora did for music: Categorize books using a bewildering set of characteristics to help people find things they want to read, from the obvious to the obscure.

Industry observers and others noted that the acquisition was meant to help Apple improve its ebook recommendations to users, another weapon it could use in its battle with Amazon. While that might be true, what I think is more likely is that Apple is preparing something bigger and more interesting.

While recommendation engines are important for online retail operations (basically performing the same function as in-store displays and trained sales people), they're much more important for content subscription services.

The key for these services is making it easy for their users to find something new to consume, especially when the service has a limited selection, like Netflix. Netflix has a smattering of original programming and headlining movies and television shows, but much of its catalog is "back-list": Movies and shows you may never have heard of or are very old. To help you, a fan of say the movie X-Men find something to watch among that catalog is very important for Netflix because there aren't enough pieces of content of that quality to keep you a happy subscriber for long. You'll quickly get bored with the service an cancel your subscription. At least that's how the theory goes.

In fact, Netflix bought into this concept so much that it famously offered a $1 million prize to anyone who could improve on its already quite effective recommendation algorithms.

Enter Apple and BookLamp. As Andrew Rhomberg points out in this post, BookLamp would be a far more valuable pickup if it powered Apple's ebook subscription service -- think Oyster, Scribd or Amazon's new Kindle Unlimited -- rather than just an add-on to iBooks.